I've searched through the stack exchange for wordpress and was unable to come up with an answer to this question. All of the wordpress codex's examples and external resources come from 2004-2006. I'd love an example of a popular Wordpress plugin that is also well-written. As I'm fairly new to programming (less than 1 year in), this would be immensely helpful.
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Take a look at the highest voted Qs on WPSE
Download some plugins from well respected developers to see how they code their stuff.